1. Field of the Invention
The present invention relates to vehicle mirror systems which may be adjusted by electrically controlled motors and, more particularly, to a potentiometer for measuring the position of the mirror glass which includes dampening properties to minimize vibrations affecting the mirror glass.
2. Discussion
In order to facilitate use of exterior mirror assemblies on vehicles, many mirror assemblies come equipped with a pair of electrical motors which may be operated within the vehicle. Electrical signals sent to the motors by an internal vehicle switch causes displacement of the motors which in turn causes displacement of the mirror glass. This facilitates adjusting the position of the mirror glass so that driver can obtain an optimum view with minimum effort. To further facilitate the use of motorized mirror assemblies for operation by the driver, some motorized mirror assemblies include a memory so that vehicle mirror or mirrors can be set to a predetermined position and the position can be memorized. The mirror or mirrors can later be automatically returned to the predetermined position for a particular vehicle operator. One or more vehicle operators can be accommodated by providing corresponding memory settings for each driver.
Mirror assembly systems having memory capabilities include one or a pair of motors to displace the mirror glass about a pivot point for the mirror glass. The motors typically include a position sensor which measures displacement of the motor to determine the position of the mirror glass. In such systems, the position sensor attaches to the motor housing at one end and to the gear train at the other end in order to measure displacement of the gear train. By arranging the position sensor in this manner, the position sensor will have inherent inaccuracies due to the play or slop in the gear train, commonly known as backlash. Such systems effectively measure the position of the motor, rather than the position of the mirror glass.
Existing systems utilize a position sensor which has no damping capability. Because exterior mirrors are subject to road vibration transmitted through the vehicle and wind vibration, such position sensing devices output a signal adversely affected by the vibration experienced by the mirror glass. The varying signal introduces inherent inaccuracy when attempting to position the mirror when the vehicle is in operation. Although the position signal output by the position sensor can be filtered, this adds to the cost of the electrical control system for the mirror assembly.
It is an object of the present invention to provide a mirror assembly having a position sensor which measures the actual position of the mirror glass.
It is a further object of the present invention to provide a mirror assembly having a position sensor for the mirror glass which is detached from the motor mechanism.
It is yet a further object of the present invention to provide a position sensor for the mirror glass which is unaffected by backlash in the motorized gear train.
It is yet a further object of the present invention to provide a position sensor having dampening properties to compensate for noise and vibration experienced by the mirror assembly.
The invention is directed to a mirror assembly for a vehicle. The mirror assembly includes a mirror housing and a reflective element. A backing assembly supports the reflective element and includes a pivot point about which the backing assembly and the reflective element pivot. An electric motor is mounted to the mirror housing and is responsive to an electrical input to displace the backing assembly and supported reflective element about the pivot point. A position sensor detects displacement of the backing assembly, and the position sensor includes a dampener to dampen movement of the position sensor.